everdrive n8 always was a bit finnicky and i've never gotten a good grip on the different firmwares and their varying degrees of support - if at all materially reasonable in your case, i would've recommended using everdrive pro or powerpak instead. But since you have the n8 and maybe not one of the other two alternatives, let's see if we can troubleshoot this one.
First off, have you used the BNROM or the GTROM version of project blue? The BNROM version has the widest compatibility and should be the one you find in the main download folder.
Secondly, just to rule things out - what system are you using the everdrive n8 on? Original NES? Toploader? Something else? (If so, which clone?)
Thirdly;
There might be an off chance that your firmware version doesn't support the possibility that BNROM games can be 512kB:s large (which they can, but no historical game used a size that large and there's a slight chance that the firmware doesn't take the theoretical max into consideration). It actually sounds like it, since a gray screen would imply a problem with loading program banks properly. It probably tries to run the program from the wrong memory bank which usually results in a cpu lock (nothing dangerous) or even some nonsensical accidental loop where data is interpreted as program code. either way, no graphics are loaded into chr ram, no specific palette is loaded into the ppu, and you get the gray screen.
This could either be resolved by trying to hack the current firmware to accept a new definition (a bit outside of my knowledge, unfortunately), or trying other firmware versions.
Optionally as a last resort, you can add GTROM support to your existing firmware by following these instructions. be careful to have a pristine firmware copy somewhere as backup before you do any edits. You'll need a hex editor such as HxD.
https://forums.nesdev.com/viewtopic.php?f=9&t=18841
if doing these modifications, you should be able to run the GTROM version of project blue on your everdrive n8. I think it's tucked away with the level editor download?
(Note that we've had some few reports of the game locking up for some unfortunate n8 users. It seems to be down to electrical circumstance with their particular setup at home. Just something to be aware of. In their cases, they've been able to play the game for a while but it eventually locks. the n8 is, unfortunately, running on the edge of electrical stability. But you should probably have experienced similar issues in other games by now, in that case. This doesn't seem to be your particular problem. )